What is commonly referred to as a tractor is a back bridge or a half bridge? What does it mean?!
A tractor is a vehicle that separates parts of a vehicle from a freight car. Such as Transformers Optimus Prime, that is tractor, and only the front, no cargo box, freight car half of the train skin that kind of super.
Bridge can be understood as a shaft (tire shaft), a shaft on both sides of the tire, such as double bridge is half of the road vehicle, front axle 2 wheel, rear axle 2 wheel, double back bridge refers to the front axle 2 wheel, rear axle has 2. Common vehicles on the 4 axis (4 bridges) are trucks.